The present invention relates to a method of plasma-processing a process object in the semiconductor processing system by using a plasma and, more particularly, to a dry etching end point detecting technique. Note that semiconductor processing refers to various types of processing operations performed in order to manufacture, on a process object, e.g., a semiconductor wafer or an LCD substrate, semiconductor devices and structures including wiring layers and electrodes to be connected to the semiconductor devices by forming semiconductor layers, insulating layers, conductive layers, and the like on the process object with predetermined patterns.
In the semiconductor device manufacturing process, dry etching is an indispensable technique in forming micropatterns. According to dry etching, a plasma is generated in vacuum by using a reactive gas, and an object portion is removed by using ions, neutral radicals, atoms, molecules, or the like in the plasma. If etching is continued even after the object portion is completely removed, the underlying material may be etched unnecessarily, or the etching shape may change. Accordingly, when obtaining a precise design structure, it is very important to accurately detect the end point of etching.
In particular, as the semiconductor integrated circuits are very highly integrated and very multi-layered recently, micropatterning of the contact holes and the like progresses. In, e.g., SAC (Self-Aligned Contact) processing, one of the technical requirements is to detect the end point of processing accurately and quickly and to reliably stop processing. From this reason, it is necessary to develop a superior etching end point detection method.
A conventional typical example of the end point detection method of this type utilizes a change in emission of a plasma observed through the transmission window of an etching chamber for end point detection. More specifically, first, plasma emission is spectroscopically analyzed to extract one or a plurality of specific emission spectra. A specific emission spectrum to be selected usually corresponds to an etching gas whose emission intensity changes in accordance with the progress of etching, or to a reaction product. Measurement data obtained from the emission spectrum are sequentially accumulated in the CPU and are subjected to predetermined arithmetic processing. This arithmetic processing includes, e.g., removal of noise in the measurement data and calculation of the average value of the measurement data. Detection values obtained by arithmetic processing are sequentially compared with reference values input in advance, and the end point is detected based on the comparison results.
In the conventional end point detection method described above, accumulation and arithmetic processing of the measurement data required for end point detection take time. In particular, since the average value of the measurement data is constantly calculated in arithmetic processing, only a detection value at a past time point can be obtained. For this reason, it is difficult to detect the end point quickly, and when the end point is detected, a desired end point has sometimes already passed. This causes so-called over-etching, making it impossible to process the process object in a desired manner.